A cyst-protein gene was identified and sequenced. The predicted protein is a 26 kDa leucine-rich protein with 5 degenerate repeats. Monoclonal antibodies were produced to other cyst and secretory proteins. The genomic organization of the H7 VSP of isolate GS/M was determined. In contrast to the tail-to-tail arrangement of two identical 1267 VSP genes, there was only one VSP H7 gene. Another closely related H7 gene was identified and sequenced. One specific area was responsible for most of the divergence between the genes. The upstream untranslated regions were practically identical. The control of VSP transcription must take account of the identical upstream regions which usually contain controlling transcriptional elements.